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寫入物件屬性

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服務通常包含屬於每個服務所支援其中一種格式的子物件。 例如，連絡人服務可支援多個抽象連絡人格式的連絡人物件。 每個連絡人物件都會依 (連絡人名稱、電話號碼、電子郵件地址等) 的相關屬性來描述。

WpdServicesApiSample 應用程式包含程式碼，示範應用程式如何更新指定 Contacts 服務之子物件的名稱屬性。 此範例會使用下列 WPD 介面。

介面 描述
IPortableDeviceService 用來擷取 IPortableDeviceContent2 介面來存取支援的服務方法。
IPortableDeviceContent2 提供內容特定方法的存取權。
IPortableDeviceProperties 用來寫入物件屬性值，以及判斷是否可以寫入指定的屬性
IPortableDeviceValues 用來保存要寫入的屬性值、判斷寫入作業的結果，以及在判斷寫入功能) 時擷取屬性的屬性 (。

 

當使用者在命令列選擇選項 「8」 時，應用程式會叫用 ContentProperties.cpp 模組中找到的 WriteContentProperties 方法。 這個方法會提示使用者輸入要更新屬性的物件識別碼。 使用者會識別 物件，而 方法會提示使用者指定新名稱。 指定這個名稱之後，方法會更新指定物件的 Name 屬性。

請注意，在撰寫物件屬性之前，範例應用程式會在連線的裝置上開啟連絡人服務。

WriteContentProperties方法的下列程式碼示範應用程式如何使用IPortableDeviceContent2介面來擷取IPortableDeviceProperties介面。 將所要求屬性的 PROPERTYKEYS 傳遞至 IPortableDeviceProperties：：SetValues 方法， WriteContentProperties 會更新 name 屬性。

void WriteContentProperties(
 IPortableDeviceService* pService)
{
 if (pService == NULL)
 {
  printf("! A NULL IPortableDeviceService interface pointer was received\n");
  return;
 }

 HRESULT          hr       = S_OK;
 WCHAR         wszSelection[81]  = {0};
 WCHAR         wszNewObjectName[81] = {0};
 CComPtr<IPortableDeviceProperties> pProperties;
 CComPtr<IPortableDeviceContent2>   pContent;
 CComPtr<IPortableDeviceValues>  pObjectPropertiesToWrite;
 CComPtr<IPortableDeviceValues>  pPropertyWriteResults;
 CComPtr<IPortableDeviceValues>  pAttributes;
 BOOL          bCanWrite   = FALSE;

 // Prompt user to enter an object identifier on the device to write properties on.
 printf("Enter the identifer of the object you wish to write properties on.\n>");
 hr = StringCbGetsW(wszSelection,sizeof(wszSelection));
 if (FAILED(hr))
 {
  printf("An invalid object identifier was specified, aborting property reading\n");
 }

 // 1) Get an IPortableDeviceContent2 interface from the IPortableDeviceService interface to
 // access the content-specific methods.
 if (SUCCEEDED(hr))
 {
  hr = pService->Content(&pContent);
  if (FAILED(hr))
  {
   printf("! Failed to get IPortableDeviceContent2 from IPortableDeviceService, hr = 0x%lx\n",hr);
  }
 }

 // 2) Get an IPortableDeviceProperties interface from the IPortableDeviceContent2 interface
 // to access the property-specific methods.
 if (SUCCEEDED(hr))
 {
  hr = pContent->Properties(&pProperties);
  if (FAILED(hr))
  {
   printf("! Failed to get IPortableDeviceProperties from IPortableDeviceContent2, hr = 0x%lx\n",hr);
  }
 }

 // 3) Check the property attributes to see if we can write/change the NAME_GenericObj_Name property.
 if (SUCCEEDED(hr))
 {
  hr = pProperties->GetPropertyAttributes(wszSelection,
            PKEY_GenericObj_Name,
            &pAttributes);
  if (SUCCEEDED(hr))
  {
   hr = pAttributes->GetBoolValue(WPD_PROPERTY_ATTRIBUTE_CAN_WRITE, &bCanWrite);
   if (SUCCEEDED(hr))
   {
    if (bCanWrite)
    {
     printf("The attribute WPD_PROPERTY_ATTRIBUTE_CAN_WRITE for PKEY_GenericObj_Name reports TRUE\nThis means that the property can be changed/updated\n\n");
    }
    else
    {
     printf("The attribute WPD_PROPERTY_ATTRIBUTE_CAN_WRITE for PKEY_GenericObj_Name reports FALSE\nThis means that the property cannot be changed/updated\n\n");
    }
   }
   else
   {
    printf("! Failed to get the WPD_PROPERTY_ATTRIBUTE_CAN_WRITE value for PKEY_GenericObj_Name on object '%ws', hr = 0x%lx\n", wszSelection, hr);
   }
  }
 }

 // 4) Prompt the user for the new value of the NAME_GenericObj_Name property only if the property attributes report
 // that it can be changed/updated.
 if (bCanWrite)
 {
  printf("Enter the new PKEY_GenericObj_Name property for the object '%ws'.\n>",wszSelection);
  hr = StringCbGetsW(wszNewObjectName,sizeof(wszNewObjectName));
  if (FAILED(hr))
  {
   printf("An invalid PKEY_GenericObj_Name was specified, aborting property writing\n");
  }

  // 5) CoCreate an IPortableDeviceValues interface to hold the property values
  // we wish to write.
  if (SUCCEEDED(hr))
  {
   hr = CoCreateInstance(CLSID_PortableDeviceValues,
          NULL,
          CLSCTX_INPROC_SERVER,
          IID_IPortableDeviceValues,
          (VOID**) &pObjectPropertiesToWrite);
   if (SUCCEEDED(hr))
   {
    if (pObjectPropertiesToWrite != NULL)
    {
     hr = pObjectPropertiesToWrite->SetStringValue(PKEY_GenericObj_Name, wszNewObjectName);
     if (FAILED(hr))
     {
      printf("! Failed to add PKEY_GenericObj_Name to IPortableDeviceValues, hr= 0x%lx\n", hr);
     }
    }
   }
  }

  // 6) Call SetValues() passing the collection of specified PROPERTYKEYs.
  if (SUCCEEDED(hr))
  {
   hr = pProperties->SetValues(wszSelection,      // The object whose properties we are reading
          pObjectPropertiesToWrite,   // The properties we want to read
          &pPropertyWriteResults); // Driver supplied property result values for the property read operation
   if (FAILED(hr))
   {
    printf("! Failed to set properties for object '%ws', hr= 0x%lx\n", wszSelection, hr);
   }
   else
   {
    printf("The PKEY_GenericObj_Name property on object '%ws' was written successfully (Read the properties again to see the updated value)\n", wszSelection);
   }
  }
 }
}

IPortableDeviceContent2

IPortableDeviceProperties

WpdServicesApiSample